1. Technical Field
The present invention relates to projectors.
2. Related Art
A projector using a discharge lamp such as a high-pressure mercury lamp or a metal halide lamp has been put to practical use. As such a projector, in JP-A-2003-102030, for example, a projector having a unit for varying the intensity of a light source in accordance with a color separation unit or the like in synchronization with a image signal is disclosed. However, JP-A-2009-237302 describes that if the intensity of the light source is simply varied, an electrode of the discharge lamp will wear out significantly.
Moreover, in recent years, a projector that outputs a stereoscopic image by using a discharge lamp such as a high-pressure mercury lamp or a metal halide lamp has been put to practical use.
One of the methods to output a stereoscopic image is a method by which switching between a image for the right eye and a image for the left eye is performed and the image for the right eye and the image for the left eye are alternately output (for example, active shutter glasses technology such as “XPAND beyond cinema” (a trademark of X6D Limited)). In this method, the right eye is made to view the image for the right eye and the left eye is made to view the image for the left eye by using active shutter glasses etc. synchronized with a image signal, whereby the image is made to appear stereoscopically by using parallax between what the right and left eyes see.
When a stereoscopic image is projected by the method by which a image for the right eye and a image for the left eye are alternately output, the amount of light that enters the right eye and the left eye is less than half of the amount of light that enters the right eye and the left eye when an existing two-dimensional image is projected. Moreover, when crosstalk by which the image for the right eye enters the left eye or the image for the left eye enters the right eye occurs, the observer loses the sense of viewing the stereoscopic image. Therefore, it is necessary to provide a period in which both active shutters are closed. As a result, when a stereoscopic image is projected by the method by which a image for the right eye and a image for the left eye are alternately output, the image appears darker than when an existing two-dimensional image is projected. To make the image appear bright, the drive power can be simply increased. However, this increases the power consumption of the projector or accelerates the deterioration of peripheral parts associated with the increase in drive power.
Moreover, if control to reduce the brightness of the discharge lamp in a period in which both active shutters are closed and increase the brightness of the discharge lamp in a period in which one of the active shutters is opened is performed to make the image appear bright, the temperature of the electrode of the discharge lamp is reduced in a period in which the brightness of the discharge lamp is reduced, resulting in inadequate fusibility of the tip of the electrode. This may cause deformation of the electrode. When the electrode is deformed, there is a possibility of, for example, the occurrence of flicker.
In particular, when a drive current of the discharge lamp becomes smaller with the progress of a deteriorating state of the discharge lamp, the brightness of the discharge lamp is reduced and the fusibility of the tip of the electrode becomes inadequate, which makes the electrode tend to be deformed. Therefore, special consideration is needed to project a stereoscopic image in such a way that the stereoscopic image appears bright while preventing deformation of the electrode.